This is off-topic, but hopefully, it'll help...
Jetcz, did you successfully install CM7? Will say, what do you see, when you are rebooting the phone?
There are three screens...
1. Galaxy S GT-I9000
2. Galaxy S & cyanogen(mod)
3. Cyanogen Mod boot animation
I made a little mistake while flashing and had some minor bugs on the phone. So I went all over again and got it finally to work. The point was, that I never saw the second screen...
Some further information if it still doesn't work.
- Which Mod of CM7 do you use? You'll find this information in "about phone" and see in "mod-version". Mine is called "CyanogenMod-7-05112011-NIGHTLY-GalaxyS".
- I know, stupid question... But are you sure you have the international version of the Galaxy S? You know, there are several variants...